In such a data processing system as an SMP computer system, a control unit is generally used for controlling data transfers and routing. The control unit connects to the dataflow. The data routing is often implemented using Multiplexors (MUX) or Selector logic with encoded controls. There is often no checking on the control signals to determine if data is properly steered through the selection logic. Also, as new buses or controls are added, the dataflow has to be re-worked. All this is troublesome.